Nearly all liquid hydrocarbon fuels are formulated with one or more of a variety of additives to enhance or impart desirable properties. The high quality of modern fuels results in part from the use of additives. The importance of additives to provide detergent properties to hydrocarbon fuel compositions, such as gasolines, is discussed in U.S. Pat. No. 4,022,589 by Alquist and Ebersole. Maintaining clean intake manifolds and other carburetor parts is important in maintaining minimum fuel consumption and minimum emissions. Needed still are fuel-soluble ashless additives of high detergent effectiveness at very low use-levels.